Manufacture of acetaldehyde by



Patented July 2, 1940 MANUFACTURE OF ACETALDEHYDE' BY HYDRATION 0F ACETYLENE Walter Henry Groombridge'and Thomas Pride Dee, Spondon, near Derby, England, .assignors I to Celanese Corporation of America, a corporation of Delaware N0 Drawing. Application April 20, 1937, Serial No. 137,980. In Great Britain August 2, 1935 r 13 Claims. (Cl. 260-605) This invention relates to'thje manufacture of acetaldehyde by hydration ofacetylene, and, is a continuation-in-part of our applications. No.

89,684 filed July 8, 1936. y l The hydration of acetylene by subjecting this compound to reaction with steam in presence of a solidcatalyst has in recentyears been the subject of a considerable amount of research as a result of which numerous catalysts have been proposed.

0 The value of any particular catalyst depends on a number of factors, including the life of the 'catalyst, the yield of usefullproducts, which are chiefly acetaldehyde possibly together with some crotonaldehyde, based on acetyleneused, the conversion s based on the acetylene passed incontact with the catalyst and the temperature atwhich optimum results are obtained.

lands been found thatwhenj working with cadmium-phosphoric acid compounds as catalysts 0 these factors are very largely'dependent -onithe form in which the catalyst is employed,"and that c it isypossible to obtain a. catalyst of this type whichwillo rateefi i I De w my mumble The acid phosphateis then decomposed to cadmium meta-phosphate by the action of heat,-this stage takin placemainl-yor entirely during the of time while giving anexceptionally good 5 yield of acetaldehyde and conversionfleven at a high rate of passage of the acetylene, and which,

moreover, gives optimum results at relatively low 1 temperatures of the order of 25.0 to 350". C. y The present invention concerns the production 0 of acadmium phosphate which givesresults as a catalyst, in the hydration of acetylene, which are much superior to those, given by other cadmium phosphates. -The catalyst of theginvention consists of cadmium meta-phosphate inthe form of a compact mass of microscopic particles. y

. The cadmium meta-phosphate is prepared by reacting a cadmium compound'iwith ortho phosphoric acid or a substance yielding ortho-phosphoric acid, i. e., with a compound containing the P04 radicle and at least three hydrogen atoms for each P04 radicle. Substances which may be used instead of ortho-phosphoricacid itself are ortho-phosphates of volatile bases. 1. e., ammonia and volatile amines, and ortho-phosphoric acid esters, particlarly compounds which. are partially alkylated ortho-phosphoric acids, namely monoand di-alkyl esters. The best results are obtained by adding ortho-phosphoric acid,- in about the I proportion needed to form the acid cadmium ortho-phosphate cdunrom. to a mm cream of finely powdered cadmium carbonate and water (for instance, 1 part by weight of cadmium carbonate to about 2 parts of water). The tempera-. ture at which the reagents are mixed should be 5 suchaato avoid the growth of large crystals,

since. the hue structure of. the resulting product would thus be impaired, with the result that a less active catalyst wouldlbe obtained. In this connection it has-beenifound, most beneficial to heat a cadmiumcarbonate; cream, suchas that .5

referred to above to aztemperature of 60-80 C.

before adding orthorphosphoric acid, which should be introduced slowly and with efficient stirring.- After introduction of the ortho-ph'osphoric acid the .mixturecontained, for instance, 10

in an iron vessel, is. evaporated to a pasty mass while continuingstirring, and then finally dried in an oven at 25%3502-(3, after which the dried product may bebrokengup-into, pieces of a size suitable for introductionfintothe catalyst cham- 16 her to be employed. .1

The formation ofthe, cadmium meta-phosphate involves the following stages: First an acid cadmium ortho-phosphate is. formed, with cadmium carbonate and ortho-phosphoric acid as 20 starting materials according to the equation:

drying at 250450? 9., according to the equation:

' cdmiron o monwzmo It would appear the flrst of these equations that any substance capable of yielding HzPO4' ions could be used in place of ortho-phosphoric acid.

Actually, however, substances yielding HaPO4' stances in general is liable to have a marked deleterious effect on the properties of the catalyst.

The properties of the catalyst mass may be enhanced by means of a sintering treatment eifect- 5' ed byheating to incipient fusion. One very important :mult of the sintering treatment is that it increases very considerably the life of the catalyst, so that it may. with suitable in tervals for reactivation, be employed for as much so as3-4 times as long as a similar catalyst which has not been subjected to the sintering treatment,

before disintegration of the catalyst renders it unfit for further use. The sinterlng treatment may also enhance the actual activity of the cataiyst, more particularly when dealing with a gas mixture containing but low percentages, e. g., 5-10% of acetylene.

When carefully prepared in the manner above described the catalyst consists, as previously indicated, of a compact mass of microscopic particles of cadmium meta-phosphate. The particles in a highly active catalyst according to the invention should be of less than0.01 mm. diameter,while yield begins to show signs of falling, and can be' carried out very eflectively by blowing a current of air over the hot catalyst for a period of 1 to 3 hours. When the catalyst shows serious falling oil in activity, and is not fully revived by such reactivation treatment, a further improvement may be effected by removing the catalyst from the reactionzone, sieving it free from dust and then returning it for re-use after it has been subjected to reactivation with air.

The amount of steam employed may be varied within wide limits, but may generally be equal to about 2 to 15 timesthe volume of the acetylene. The strongly exothermic nature of the reaction permits the use of the larger quantities of steam without rendering necessary the external applieflicient hydration of the acetylene contained in commercial gas mixtures,.such as are obtained in the cracking of hydrocarbons and which contain but low percentages of acetylene, e. g., less than 10%, without previously separating or concentrating the acetylene. Preferably the diluting gases should be hydrogen or hydrocarbons, such as methane.-

The following examples illustrate the invention:

Example 1 516 parts -=(by weight) of finely powdered cad-3 mium carbonate are made intoa cream with 1000 parts of water. The mixtureis heated to 70 C. in a copper vessel and 665 parts of ortho-phos phoric acid of sp. gr. 1.75 are slowly added with eflicient stirring. When all the phosphoric acid has been added the mixture is evaporated to a pastymass, the stirring operation being continued throughout this evaporation. The product is then dried in" an. oven at 300 0., broken into pieces of a size suitable for use in the subsequent catalytic process, and the pieces subjected to a sinterlng treatment by heating in an iron vessel to-th e point ofincipient fusion.

. Example 2 Acetaldehyde is produced by passing a mixture of acetylene and hydrogen containing 7.8% of acetylene together with steam over the catalyst prepared in Example 1 and maintained ata reaction temperature of 250 to 260 C.

The rates of passage of the acetylene-hydrogen mixture and of the steam are about 1200 and 650 litres per litre of catalyst perhour respectively.

Example 3 Acetaldehyde is produced by passing pure acetylene and steam over a catalyst prepared as in Example 1 at a temperature of 350 C., the rates phate produced as a compact mass of microscopic particles by reacting a compound containing the P04 radicle and at least three hydrogen atoms for each P04 radicle and a cadmium compound, in about the proportions needed to form the acid cadmium ortho-phosphate Cd(H2P04) z, in an aqueous medium, evaporating water from and heating the reaction product so as to form the meta-phosphate.

2. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction with steam in presence of cadmium meta-phosphate produced as a compact mass of microscopic particles by reacting ortho-phosphoric acid and a cadmium compound, in about the proportions needed to form the acid cadmium ortho-phosphate Cd(H2PO4)z, in an aqueous medium, evap crating water from and heating the reaction products so as to form the meta-phosphate.

3. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction with steam in presence of cadmium meta-phosphate produced as a compact mass of microscopic particles by reacting an ortho-phosphate of a volatile base and a cadmium compound, in about the proportions needed to form the acid cadmium orthc-phosphate Cd(H2PO4)z, in an aqueous medium, evaporating water from and heating the reaction product so as to form the meta-phosphate,

4. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction with steam in presence of cadmium meta-phosphate produced as a compact mass of microscopic particles by slowly adding ortho-phosphoric acid to a thin cream of finely powdered cadmium carbonate in water, maintained at 60-80 C., the acid and carbonate being employed in about the proportions needed to form the. acid cadmium ortho-phosphate Cd(HaPO4)a, evaporating to a pasty mass, efllcient stirring being maintained during the addition of phosphoric acid and subsequent evaporation, and heating the product to 250-350 C. so as to dry it and to form the metaphosphate.

5. Process for the productionof acetaldehyde, which comprisessubjecting acetylene to reaction withsteam in presence of cadmium meta-phosphate produced as a compact mass of microscopic particles by reacting a compound containing the P04 radicle and at least three hydrogen atoms for each P04 radicle and a cadmium compound, in about the proportions needed to form the acid cadmium ortho-phosphate Cd(I-I2PQ4)2, in an aqueous medium, evaporating water from and heatingthe reaction product so as to form the ing treatment.

7. Process for the production of acetaldehyde, which. comprises subjecting acetylene to reaction with steam in presence of cadmium metaphosphate produced as a compact mass of microscopic particles by reacting an ammonium orthophosphate and a cadmium compound in about the proportions needed to form the acid cadmium ortho-phosphate Cd(HzPOi) 2, in an aqueous medium, evaporating waterfrom and heating the reaction product so as to form the meta-phosphate and subjecting the meta-phosphate to a sintering treatment.

8. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction. with steam in presence of cadmium meta-phosphate produced as a compact mass or microscopic particles by reacting a partially alkylated ortho-phosphoric acid and a cadmium compound in about the proportions needed to form the acid, cadmium ortho-phosphate common 2, in an aqueous medium, evaporating water from and heating the reaction product so as to form the meta-phosphate and subjecting the meta-phosphate to a sintering treatment.

9. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction with steam in presence of cadmium meta-phosphate produced as a compact mass of microscopic'particles byslowly adding ortho-phosphoric acid to a thin cream orflnely powdered cadmium carbonate in water, maintained at Git-80 0., the acid and carbonate being employed in about the proportions needed to form the acid cadmium ortho-phosphate Cd(H:PO4)2. evaporating to a pasty mass. eflicient stirring being maintained during the addition of phosphoric acid and subsequent evaporation, heating the product to 250350 C. so as to dry it and to form the meta-phosphate and subjecting the metaphosphate to a sintering treatment.

10. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction with steam in presence of cadmium meta-phosphate in the form of a compact mass of micro scopic particles.

11. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction with steam in presence of sintered cadmium of particles, the majority of which are .of less than 0.01 mm. diameter. i

12. Process for the production of acetaldehyde, which comprises subjecting acetylene to reaction with steam in presence of cadmium meta-phosphate produced as a compact mass of particles, the majority of which areof less than 0.01 mm. diameter, by slowly adding ortho-phosphoric acid meta-phosphate in the form of a compact mass to a thin cream of finely powdered cadmium carbonate in'water, maintained at 60-80 0., the acid and carbonate being employed in about the proportions needed to form. the acid cadmium ortho-phcsphate Cd(H2PO-i)2, evaporating to a pasty mass, eflicient stirring being maintained during the addition of phosphoric acid and subsequent evaporation, and heating the product to 250-350 C. so as to dry it and to form the metaphosphate;

13., Process for the production of I acetaldehyde which comprises subjecting acetylene to reaction with steam in presence of cadmium meta-phosphate produced as a compact mass of particles, the majority of which are of less than 0.01 mm. diameter, by slowly adding ortho-phosphoric acid to a thin cream of finely powdered cadmium carbonate in water, maintained at Gil-80 C., the acid and carbonate being employed in about the proportions needed to form the acid cadmium ortho-phosphate CdG-IzPOOz, evaporating to a pasty mass, eflicient stirring being maintained during the iddition of phosphoric acid and subsequent evaporation, heating the product to 250-350 C. so as to dry it and to form the metaphosphate and subjecting the meta-phosphate to a sintering treatment. a 1

WALTER HENRY GROOMBRIDGE. THOMAS PRIDE DEE. 

